During the initial make-up of drilling fluids viscosified with sepiolite clay minerals, the slurry is very thin because the fibers of the clay particles have not separated sufficiently. In order to provide a drilling fluid with sufficient viscosity to support drill solids and weighting materials, large amounts of shearing energy by mechanical mixers must be used in the mud pits to separate these bundles of fibers. In lieu of such mechanical mixers, the shearing energy can be achieved by circulation of the drilling fluid through the drill pipe, bit and annulus. This is not always practical because of drilling fluid weight considerations.
Alternatively, small amounts of bentonite, up to five pounds per barrel can be used. This is sometimes not desirable because of the subsequent inferior performance of bentonite as the mud reaches temperatures above 400.degree. F. and the necessity of fresh water pre-hydration of the bentonite.
Accordingly, it is an object of the invention to provide a viscosifier for drilling fluid that can be used in all types of water and can be used at high temperatures.
Another object of the invention is to provide a clay extender which will impart to a slurry of the sepiolite clay during initial make-up, a viscosity of sufficient nature to support a weighting agent without the need of excessive shearing energy.